PostScript, PDF & Ghostscript Learning Projects

Master the Document Processing Pipeline: From understanding PostScript as a stack-based programming language that draws, to PDF as a structured document format, to Ghostscript as the transformation engine between them.

Overview

This collection of projects takes you through the complete document processing pipeline. You’ll understand what really happens when you “print to PDF,” why these formats were designed the way they were, and how production-grade document processors work at a systems level.

The Key Insight

PostScript is a program that draws; PDF is a static snapshot of what was drawn.

When you click “Export as PDF” or “Print to PDF,” here’s the real flow:

Application → PostScript Program → Interpreter → PDF Output
                    ↓
            Stack-Based Virtual Machine
                    ↓
            Graphics State Machine
                    ↓
            Choose Output Backend (PDF, PNG, Printer)

Projects

#	Project	Difficulty	Focus Area	Time Estimate
1	PostScript Subset Interpreter	Advanced	Interpreters / Graphics	2-3 weeks
2	PDF File Parser & Renderer	Advanced	Document Formats / Compression	3-4 weeks
3	PostScript-to-PDF Converter	Expert	Code Generation / Graphics	1 month+
4	Ghostscript Source Code Exploration Tool	Advanced	Document Processing / Code Analysis	2-3 weeks
5	PDF Assembly Language	Intermediate	Document Processing / DSL Design	2-3 weeks
6	Document Processing Pipeline (Capstone)	Expert	Full Stack / Systems Design	2-3 months

Learning Path

Recommended Order

┌─────────────────────────────────────────────────────────────────┐
│  PROJECT 1: PostScript Interpreter                              │
│  Understanding: PostScript is EXECUTED to produce graphics      │
└──────────────────────────┬──────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────────────┐
│  PROJECT 2: PDF Parser & Renderer                               │
│  Understanding: PDF is STRUCTURED data (frozen PostScript)      │
└──────────────────────────┬──────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────────────┐
│  PROJECT 3: PostScript-to-PDF Converter                         │
│  Understanding: How EXECUTION becomes STRUCTURE                 │
└──────────────────────────┬──────────────────────────────────────┘
                           │
              ┌────────────┼────────────┐
              ▼            ▼            ▼
         PROJECT 4    PROJECT 5    PROJECT 6
         (Explore     (Build       (Full
         Production)  Your DSL)    Pipeline)

Start with Project 1 (PostScript Interpreter) - Foundational insight that PostScript is executed to produce graphics
Then do Project 2 (PDF Parser) - See what the output looks like; notice PDF operators mirror PostScript
Then tackle Project 3 (PS-to-PDF Converter) - Connect execution to output; understand the transformation
Choose your path: Explore production code (P4), build tools (P5), or go for the capstone (P6)

Core Concepts

Concept	What You Need to Internalize
Stack-based execution	PostScript is a stack machine. Every operation pops arguments and pushes results.
Graphics state machine	Drawing operations modify state (path, matrix, color, font). `gsave`/`grestore` save/restore state.
Transformation matrix (CTM)	All coordinates pass through a 2D transformation matrix.
PostScript as language	PostScript is Turing-complete with procedures, conditionals, loops.
PDF object graph	PDF is numbered objects with references. The xref table enables random access.
Content streams	PDF pages contain content streams—sequences of PostScript-like operators.
PS→PDF transformation	Converting PostScript to PDF means executing the program, capturing operations, serializing as PDF objects.

Historical Context

Year	Event	Impact
1984	PostScript invented	Desktop publishing revolution; universal printer language
1988	Ghostscript created	Open-source PS interpreter; enabled Linux printing
1993	PDF invented	“PostScript without programming”; universal document exchange
2021	Ghostscript 9.55	PDF interpreter rewritten in C (2-3x faster, better security)

Technology Stack

Primary Language: C

Systems-level control for interpreters and parsers
Direct memory manipulation for performance
Integration with graphics libraries (Cairo, libpng)

Alternative Languages

Python: Rapid prototyping, PDF manipulation (pypdf, pikepdf)
Rust: Memory-safe systems programming
Go: Fast development with good library support

Key Libraries & Tools

zlib: Stream compression/decompression
Cairo: 2D graphics rendering
Ghostscript: Reference implementation
qpdf: PDF validation and manipulation

Book References

PostScript & Graphics

PDF

Implementation

Project Comparison

Project	Depth of Understanding	Fun Factor	Business Potential
PS Interpreter	⭐⭐⭐⭐ (PostScript execution)	⭐⭐⭐⭐	Resume Gold
PDF Parser/Renderer	⭐⭐⭐⭐ (PDF structure)	⭐⭐⭐	Service & Support
PS-to-PDF Converter	⭐⭐⭐⭐⭐ (full pipeline)	⭐⭐⭐⭐⭐	Service & Support
Ghostscript Explorer	⭐⭐⭐⭐ (production implementation)	⭐⭐⭐	Educational
PDF Assembly Language	⭐⭐⭐⭐ (PDF internals)	⭐⭐⭐⭐	Micro-SaaS
Document Pipeline	⭐⭐⭐⭐⭐ (complete system)	⭐⭐⭐⭐⭐	Full Product

Getting Started

Choose your starting project (recommended: Project 1)
Read the prerequisite concepts in the project file
Complete the thinking exercises before coding
Follow the hints in layers when stuck
Validate against production tools (Ghostscript, qpdf, pdfinfo)

Each project file contains:

Learning objectives
Deep theoretical foundation
Solution architecture
Implementation guide
Testing strategy
Interview preparation questions
Recommended reading order